German Pat. No. 179,358, German application specification (Offenlegungsschrift) No. 1,482,303 and Swedish Pat. No. 349,841 show a so called hose valve which is suitable for being used as an outlet valve for a vacuum closet and which comprises a resilient and flexible hose-like member surrouned by a control chamber, wherein over- or underpressure can be created in order to close or open the valve. Generally, the aim is to design such a valve so that it, when connected to a vacuum sewer, is automatically kept closed by the underpresure in the vacuum sewer. In this case, no overpressure is needed to close the valve. When the valve is to be opened, it is only necessary to connect the control chamber to the vacuum system of the sewer. However, this kind of valve has not proven to be reliable, as malfunction may occur and as the valve does not always close quite tightly. In vacuum sewer systems, it is of great importance that all connections to the vacuum sewer are completely tight when closed. Hence, the use of valves which are not quite reliable especially with respect to tight closing must be avoided.